This invention relates to multiple magnification video inspection apparatus, and more particularly to novel means for selecting one of a plurality of different pattern reticles for projection onto a workpiece that is being inspected by the apparatus. Even more particularly this invention relates to novel reticle pattern selecting means which are particularly suitable for use in connection with multiple magnification apparatus of the type which employs a single magnification reticle projector system.
Heretofore it has been common to employ in video inspection apparatus reticle projection devices which project a reticle pattern or target onto a workpiece that is being inspected. For example U.S. Pat. No. 5,619,031, which is owned by the assignee of this application, discloses multiple magnification inspection apparatus having a reticle projector system the magnification of which is adjusted simultaneously with the image of a workpiece. On the other hand, U.S. Pat. Nos. 5,668,665 and No. 5,389,774 both of which are also assigned to the assignee of the present application, disclose inspection apparatus which employ a fixed magnification reticle projector in combination with apparatus which permits a variety of magnifications of an inspected workpiece, the fixed reticle projector thus having a range of magnifications to satisfy.
Typically, reticles of the type described above comprise a transparent disc or plate having inscribed or otherwise formed thereon, or therein, a plurality of lines or spots forming a pattern which is projected onto a workpiece that is being inspected. Still other such apparatus has employed computer generated patterns or LCD (liquid crystal display) patterns which can be turned on and off electronically, but no such prior devices have been designed to have means for selecting different patterns suitable for use with different magnfications of the inspection apparatus.
Accordingly, it is an object of this invention to provide for variable magnification video inspection apparatus novel means operable to select and to project onto a workpiece a different reticle pattern each time the magnification of the image of an inspected workpiece is changed.
A more particular object of this invention is to provide for inspection apparatus of the type described a plurality of different reticle patterns at various scales which can be elected and projected onto a workpiece to satisfy different magnifications of the apparatus.
Still a further object of this invention is to provide for variable magnification video inspection apparatus a variety of reticle patterns which can be electronically or mechanically selected and projected onto a workpiece in response to variations in the magnification of the apparatus.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.
In the reticle projector of the multiple magnification video inspection apparatus made according to one embodiment of this invention, the reticle comprises a liquid crystal display (LCD) module which is driven by a conventional plug-video card that forms part of a CPU. The CPU operates to generate signals that select the size of the pixel dots that are to be illuminated in the central viewing area of the reticle. The pixels are arranged in intersecting horizontal rows and vertical columns in the viewing area, and as the magnification setting of the apparatus is changed, the CPU can be programmed to cause a corresponding change in the size of the pixels that would be energized. The energized pixels form clear or transparent dots on the reticle, while the remaining, unenergized pixels cause corresponding areas of the reticle to remain opaque or nearly opaque. The reticle thus functions as a video monitor.
In a second embodiment the reticle is provided with a plurality of viewing areas of different size, each area comprising a plurality of small circular or rectangular openings or transparencies of equal size, the openings in each field again being arranged in spaced, parallel rows and intersecting columns. In the embodiment illustrated the reticle includes five progressively larger fields having progressively larger openings, the smallest field measuring approximately 2 by 1.5 mm., the largest field measuring approximately 132 by 24 mm., with the remaining three fields being placed adjacent to one another between the smallest and the largest fields. Depending upon the selected magnification of the apparatus, the reticle is shifted laterally of the reticle projector housing, either manually or under control of the CPU, in order selectively to place the center of any one of the five different fields into registry with the axial centerline of the reticle projector. In this way when the magnification is changed a corresponding change in the size of the openings of the projected reticle image can also be changed.